Interfacial adhesion of fluoropolymer composites to commercial copper foils subjected to aqueous photolithographic processes

Three commercial copper foils containing various degrees of surface roughness and a chemically similar surface treatment were laminated to a fluoropolymer composite and also subjected to water-based photolithographic and stripping processes. Surface analysis performed on the processed foils indicated that the highly basic pH of the stripping process was effective in removing zinc oxide, a component of the surface treatments on these foils. Morphologically, however, the surfaces did not seem to change. Ninety degree peel measurements of the resulting interfaces with and without a photoresist processes showed that the resulting practical adhesion seemed to be mainly controlled by mechanical interlocking and to a lesser amount, by chemical factors. When 50 μm wide lines were subjected to the photolithographic process and a full fabrication sequence, adhesion variability seemed to be affected by interfacial attack of the fluoropolymer/metal foil interface by the alkaline medium of stripping and other process chemicals. Reliable interfacial adhesion of narrow lines is only possible when process parameters have been optimized